Clinical Correlation between Muscle Damage and Oswestry Disability Index Score after Open Lumbar Surgery: Does Open Surgery Reduces Functional Ability?

STUDY DESIGN: Single-surgeon, single-center prospective study with prospective data collection. PURPOSE: To clinically evaluate muscle damage after open lumbar surgery and its relationship to functional activity and to validatethe improvement in function as indicated by improved Oswestry Disability Index (ODI) score despite muscle damage. OVERVIEW OF LITERATURE: Few studies have analyzed the functional loss and recovery pattern of muscles after open lumbar surgery. METHODS: The study included 30 patients who underwent open lumbar spine fusion surgery at our institution between August 2013 and May 2015. Preoperatively and at 6 months postoperatively, the patients were subjected to functional, biochemical, electrophysiological, and radiological assessments as outpatients, and the results were compared. RESULTS: Mean preoperative and 6-month postoperative values were as follows: creatine phosphokinase levels, 133.07±17.57 and 139±17.7 U/L (p <0.001); Visual Analog Scale scores for backache, 6.73±0.88 and 3.27±0.96 (p <0.001); and ODI scores, 41.6±5.51 and 22.4±4.48 (p <0.001), respectively. Preoperatively, electrophysiological studies showed that 20% of the patients had a polyphasic configuration whereas at 6 months postoperatively, all patients had polyphasic configuration (p <0.001). The mean cross-sectional area of the multifidus observed using magnetic resonance imaging (MRI) decreased from 742.67±76.62 mm(2) preoperatively to 598.27±66.38 mm(2) 6 months postoperatively (p <0.001), with all the patients exhibiting grade 2 atrophy. CONCLUSIONS: Open lumbar fusion surgery resulted in significant damage to the lumbar paraspinal muscles, as indicated by a reduction in the cross-sectional area of the multifidus by MRI and denervation of the multifidus demonstrated using electromyography. Nevertheless, the patients reported reduced back pain and improved quality of life, which may have been due to increased stability of the previously unstable lumbar spinal segment after the surgery.